Photoluminescent conjugated polymer nanoparticles (CPNs) are currently viewed as attractive alternatives to Quantum Dots (QDs) for applications ranging from biological imaging to consumer electronics.
QDs have previously shown promise in a number of in vitro and in vivo bioimaging applications, where they can be internalized by cells, allowing individual organelles to be stained. However, their potential for in vivo oxidative degradation, which can release toxic heavy metal species (e.g. cadmium and lead), ultimately precludes their use in humans or in long-term cell-tracking applications. Moreover, the use of such heavy metals is heavily restricted in certain territories, thereby underlining a need for less-toxic alternatives.
CPNs exhibit many of the desirable properties of QDs, including a small size (ca. 10-200 nm), photostable photoluminescence tunable across the visible spectrum, and the ability to be isolated as stable dispersions in water, whilst avoiding many of the toxicity-related drawbacks.
Behrendt et al. (Polym. Chem., 2013, 4, 1333-1336) discloses that replacing a proportion of the alkyl side chains present on polyfluorene non-cross-linked co-polymers with a more hydrophilic side chain has a significant influence on the size and optical properties of the resulting non-cross-linked CPNs.
Behrendt et al. (J. Mater. Chem. C, 2013, 1, 3297-3304) discloses hybrid inorganic-organic composite nanoparticles formed from polyfluorene having pendant triethoxysilyl side chains that are cross-linkable under basic conditions.
CN101323781A discloses nano-fluorescent microspheres having an outer shell made from a water-soluble polymer and an inner shell being a conjugated fluorescent structure, and cross-links between the inner and outer shells.
Zhang et al (Gaofenzi Xuebao (2013), (4), 426-435) discloses the preparation of chiral and fluorescent nanoparticles of hyperbranched conjugated polymers by solvent chirality transfer technology.
In spite of the advances made to date, it is necessary that limiting factors in the more widespread exploitation of phohotoluminescent CPNs be addressed before they can realize their full potential as a replacement for QDs. Amongst these are improved production processes, greater manufacturing control, and superior purity for use in biological applications.
The present invention was devised with the foregoing in mind.